Mick McCarthy brought his six-year tenure at Ipswich Town to a dramatic end, announcing "I'm out of here" after a 1-0 win over Barnsley on Tuesday.
The 59-year-old was due to leave the Championship club at the end of the season, but departed four games early.
It came after he was asked in his post-match news conference about fans' negative reaction to debutant Barry Cotter being substituted.
"I won't have to listen to that again, that's my last game," McCarthy said.
"I'm out of here."
The club's head of coaching and player development Bryan Klug will take charge of the first team for the remaining games of the season, with owner Marcus Evans saying he does not expect to appoint a new manager before the end of the campaign.
Ipswich said last month the former Sunderland and Wolves boss McCarthy would leave when his contract expired at the end of the campaign.
But McCarthy told the club website that an agreement was reached at the weekend to leave after Tuesday's game.
"I said I would see the season out but it's been a new experience and it's not one I have been enjoying to be honest," he said.
"I have continued to do my job to the best of my ability but there is something missing and I'm not comfortable with that.
"I have had a great time here and worked with some great people and to all those who have given me wonderful support over the last five and a half years - and there are many - I want to put on record my personal thanks."
McCarthy, who was the longest serving manager in the second tier, confirmed he would be "looking for a new challenge elsewhere".
Assistant manager Terry Connor has also left the Portman Road side, who are 12th in the table and travel to Nottingham Forest on Saturday.
'Numbskulls and driverless cars'
It should perhaps not come as a surprise that McCarthy has opted to leave ahead of schedule after a difficult final season in Suffolk.
In February he issued an apology after cameras caught him swearing in the celebrations of his side taking a late lead at rivals Norwich. The Canaries came back to equalise and McCarthy denied he had directed his language towards his own fans.
When his departure was announced in March he claimed that some "numbskull" supporters had ruined home games this season.
After the 2-2 draw at Millwall on Easter Monday he admitted a part of him had "died" after his exit was confirmed and that he felt like he was in a driverless car.